Heenan U.S. Pat. No. 3,332,327 ('327), Balint U.S. Pat. No. 3,409,344 ('344) and Suhr U.S. Pat. No. 3,984,175 ('175) each disclose a reflective pavement marker having a shell-like housing of synthetic resin, such as acrylic, with a reflective portion of light transmitting material formed with retro-directive reflector elements of the cube corner type.
The optical properties and principles of cube corner reflex reflectors are set forth in the Heenan '327 patent, particularly in connection with the description of FIG. 4 thereof. The entire disclosure of the Heenan '327 is incorporated herein by reference.
As disclosed in the Heenan '327 patent, the light receiving obverse face 40 is substantially flat with the cube corner reflective elements 50 formed on the reverse face. The light rays from oncoming vehicles are reflected back to the vehicle from each of the cube corner reflective elements. The reflected light rays of the cube corner elements are generally parallel to each other.